Method for packaging meat



July 7, 1959 K. R. NlcKoLLS METHOD FOR PACKAGING MEAT Filed July 2. 1958 IN VEN TOR.

United.

Ihe invention relates to a method for packaging Sand storing fresh meat products.

In the so-called self-service meat departments of grocery i stores, fresh vmeats such v as steaks, chops, roasts, 'hamburger, fresh dish, fresh poultry', etc. are placed vin shallow wooden or paper trays and wrapped withal clear, transparent, thermoplasticlm such as cellophane which is heat-sealed, usually on the bottom ofthe tray.' The purchasers of such sealed .meat packages will frequently store the packages inthe freezing compartment-of a household refrigerator or freezer. Y

The above noted method of packaging and storing fresh meat products is subject to certain shortcomings. 'Ivhe tray employed is usually permeable\to. air' and. water vapor; consequently, unless the-tray is1comp1ete1y -enveloped in the thermoplastic film, the package` will be able to breathe and the meat product contained therein may have: a. shortertora'gelifethan expected-.12. Even if the package is frozen, the meat product-may become dehydrated during storage, i.e., suffer from' "freezerburn When the meat package is 'frozen in the 'consumers home, there is frequently a considerable interval'between the time when the package 'is removed from a refrigerator at the store'and placed in the consumers freezer.` AIn this time interval, vthejmeat may Warm up and exude meat juices which penetrate the tray. When the meat package is subsequently frozen, the'meat becomes firmly bonded to the frozen tray and vcannot fbes'eparated therefrom until it `issubstantially "completely thawedf This delay can be an annoying and unnecessary inconvenience to the housewife, since many meats can be placed in the cooking utensil before they are thawed. In addition, the absorption of meat juices by the tray impairs the quality of the meat.

It is an object of this invention to provide an improved method for packaging fresh meat products.

Another object of this invention is to provide an improved sealed meat package which is substantially impermeable to air and Water vapor.

A further object of this invention is to provide an improved sealed meat package in which the meat will not become bonded to the package when the meat is frozen.

Other objects and advantages of the invention will be apparent from the following detailed description thereof when read in conjunction with the attached drawings in which:

Fig. 1 is a perspective view of a meat package prepared by the method of this invention;

Fig. 2 is a vertical section taken through the package of Fig. 1; and

Pig. 3 is a schematic view, partially in section, of a method for preparing the laminar plastic sheet used in the manufacture of the trays employed in the method of the present invention.

The above and related objects are attained by placing c a fresh meat package in a lightweight plastic tray and tightly enveloping and sealing said meat product and tray in a thin, transparent, heat-scalable, thermoplastic lm ,preferably f less A than about 0.01.

2,893,877: Patented July 7, 1959 which a majority of the cells have a diameter of less than about 0.02" and the skins or surface laminae of the laminar sheet consist of a styrene polymer having a density of atleast 201bs./ft.3.

Referring to Figs. land 2 of the drawings, a fresh meat product' 12, eg., hamburger, is placed in a lightweight plastic tray 10 and both the hamburger and the tray are completely enveloped and sealed with moisture proof cellophane 14. The tray 10 consists of alaminar sheet in which the core section 11 consists of a styrene polymerfoam and the skins 11a and 11b consist of an unfoamed styrene polymer. The core section 11 is approximately 0.100 thick and consists of a styrene polymer foam having adensity of about 6 lbs./ft.3 and a closedcell structure in which the majority of the cells have a diameter of about 0.01".

The skins 11a and 11b are approximately 00001-0001 thick Aand consist of'either an unfoamed styrene polymer or a styrene polymer foam having a density of at least .2 0 lbs./ft.3.

The trays employed in the invention are fabricated from a laminar sheet in which the core consists of a styrene polymer foam having a density of less than about 10 lbs/ft.3 and a closed cell structure in which a majority of the cells have al diameter of less. than about 0.02 and p. In a preferred ern lbodimentof the invention the styrene polymer foam core has a densityv of substantially less than about 10 lbs./ft.3, eg., less thanabout 6 lbs/ft.3 and more especially less than about .4 lbs./ft.,3. The skins or surface larninae of the laminar sheet consist of either an unfoamed styrene polymer or a styrene polymer foam having a density of *greater than 20 lbs./ft.3-. In one embodiment of the in- `facelamnae will vary in thickness from about 0.0001" to about 0.003. The trays of the invention, despite their light Weight, are remarkably exible and rugged. Moreover, the trays have low vapor transmission characteristics and this property insures a Water and vapor tight package even if the scalable thermoplastic film does not completely encase the bottom of the tray.

'Ihe laminar sheets employed in the manufacture of the meat trays can be prepared by cementing 0.0001- 0003" thick sheets of either an unfoamed styrene polymer or a styrene polymer foam having a density of at least 20 lbs/ft.a to both surfaces of a 0050-0200" thick core sheet of a foamed styrene polymer having a density and cell structure Within the limits previously described. Unfoamed and high density foamed styrene polymer sheets having the necessary thickness for use as skins can be prepared by blow extrusion techniques. Unfoamed styrene polymer sheets in at least certain thicknesses Within the scope of the invention are commercially available. Foamed styrene polymer sheets having the required density and cell structure for use as the core sheet can be prepared by the method disclosed in U.S. 2,797,443.

Alternatively, the laminar sheets can be prepared directly by the extrusion method illustrated in Fig. 3. In lFig. 3, a mixture of parts of polystyrene, 5-8 parts of pentane and 2-3 parts of water (to provide the desired cell size) is delivered by an extruder (not shown) into an extruder die 20 in a uid state above its melting point, but foaming within vthe extruder and the extruder dieV is suppressed by` .maintaining .thesplastic .masssunder pressure. When the plastic mass is extruded in sheet form through orifice 2,2, lthe sudden pressure drop n(ex-- truder pressure to iatmosphericpressure) causes rapid foaming of sheet 11. iOriiice :22: positioned @very close tothe nip of rolls 2.6-26fand as fafffr'esulhshe'et 11 contacts the r'ollsbefore it haslcompletelyl foarnd. In passing` through theA nip of 4the rol1s,fthe` 'surfacesffof the sheet are cooled and the expansion of lthetresinforces Ythe sheet 'into pressured engagement with" the" 'rollsfthereby providing thin skins 11a and 11bof-an essentially unfoamedpolystyrene on the foamedwstyrene-polymer sheet 11. VThe foamed contacting surfaces-of rol-ls 26-26 are cooled by-circulating cooling water' through the liquid chambers 27--27 provided therein.

The laminar sheets above described canrbefabricated intoV trays by numerous conventional-techniques,finclud ing the well-known -vacuum Vdrape-formingtechnique.

The styrene foams'which maybe -employed*as'1the core of the laminar sheets are foams -of either-styrene homopolymers or interpolymers of styrenefcontaining a predominant proportion of styrene,'i.e.-, greater -thanSO weight percent and preferably greater than 75 vweight percent styrene. Examples of monomers --thatlmay be yinterpolymerized with thestyrene include 'the conjugated 1,3-dienes, eg., butadiene, isopreue, 'etc.,alphabe`ta unsaturated monocarboxylic acids and derivativesthereof, eg., acrylic acid, methyl acrylate, ethylacrylate; butyl acrylate, 2-ethylhexyl acrylate, andthe corresponding esters of methacrylic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile; divinylbenzene,A etc. If desired, blends of -the styrene polymer with -otherepolymers may be employed, eg., blends of Athe'ystyrene polymer with rubbery diene polymers or theanalogous-compositions obtained by polymerizing styrene `-mono'n'rc-.r in the presence of a nubbery diene polymer.

In any of the above type resns,all or aportion'of the styrene may be replaced with its closely related Yhomo logues such as alpha-methylstyrene, o, p, and ni-methylstyrenes, o, m, and p-ethylstyrenes, 2,4-dimethylstyrene, etc. In genera-1, the styrene polymers' employed should have a molecular Weight in the range of .about 40,000-80,000 (as determined by the Staudingermethod). The styrene polymers included in fthe Yskins 4or surface laminae of the laminar `sheetare of.'.the 4same type as includedY in the core ofthe larninarfsheetV and above described.

ployedvto` wrap-.fthestrayand meat maybe any of. the

well-known polymeric lms presently employed for wrapping meat, cheese, etc. Examples of suitable materials include moistureproof cellophane, rubber hydrochloride films, vinylidene chloride copolymer films, oriented polyethylene -terephthalate lrns,n polyethylene lms, etc. All of these lms have suitably V low vapor transmission characteristics.`

The above descriptions and particularly the examples and the" drawings are. set-forth'. for Ypurposes of illustration only. Many other variations and modifications thereof will bc apparent to Vthose skilled in the art and can be made vll"withoutdeparting -from v`the spirit and scope of the invention hereinA described.

This application is a continuation-impart of my copending application, S.N. 628,435, filed December 14, 1956, now abandoned.

wvh'atiis claimed is:

A method for packaging..alrfreshsmeatfproduct-which eomprisingplaeing. afreshimeatprduetin a lightweight yplastic ftrayand;itightlyenveloping'and: sealing said' fresh vmeat product-...endl tray in; a'fthin,"atransparent,zheatsea1 fable'l thermoplasticzflmhavingflow; vapor `transmission charactesticsgosaid lightweight plasticV .tray` consisting of ai' laminarsheeti'r'infwhich -the corelis fa sheet `ofstyrene 4polymerilfoam' having f a density; of'- less than `about 10 -lbs'.7ft.3:andialclosedcellstructure in'which the majority of cells Yhave a diameter` of -lessithaniabout 0:0 :andrtheftopl and bottomlsskins .are .a styrene; polymerthavtin-g a densitWofr-atleast'QO lbsjft; asaid top= and bottom skins ,of'gsaid laminar.sheet-I beingY L'about l 0;0001'0.003" thick ,ltheifoamed y'styrene-.4polyrn'er y-izo're ofl-said= 4laminar :sheetfbeingfaboutinrosa-0.200"Ethiek.

.f References `-Citedain;the:iileroii-.tl'iis patent UNITnDfsTArEs rAT-nNrs 254,851,608 Cheyneyet al. -"Oct, 11, 1949 ,22,536,639 Guyer. v Jan; 2,1951 72,167,436 .,Nolandet l0ct. 23; 1956 2,770,406 Y.Lane. .c .e....New 13, v19-56 IOTHERfLREFERENCBS "ModernPacla-Lging, September'19'50,` page 931. "fMdern' Packaging, November `v 1954; page 230, article entitled P'olystyr-,ene vFoam'Insulares":Meat 'Patti'es 

